There are countless variations of Free and Shareware variations which one can find on the net to download.
Here are some programs for Windows.

logo Sokoban YASC

Very comfortable play and gui distinguish this program from the rest. The OpenSource project has a lot of unique functions.

Sokoban YASC (YetAnotherSokobanClone) comes close to the ideal Sokoban program. You can store YASC format and *.sok formated solutions, and also partial solutions within the level file itself. Level sets in *.xsb format can be read in and be played. Internal solutions are stored in the YASC format.

The program is configureable in all Features, all current Skin formats are supported. It also has a nice editor to construct user made levels, export and import functions, attractive, scaleable Skins as well as a Replay fuction for relaxed levels not to forget lapels fashion enrich this. Sokoban YASC is truly a great program!

SOKOBAN project recommends Sokoban YASC!

logo Sokofan

Sokofan brings everything what belongs to a good Sokoban program. It has such an easy interface that even a child can use it. A zuschaltbares coordinate system in the field is as a small extra is a welcome novelty.

Con: The Skin editor has not matured yet.

logo SokoFun

From Games4Brains, sokofun has a Movie function to allow playback of solutions. In the full version, SokoFun offers a high-quality editor to the construction and treatment of own level sets. Sokofun has it's own level format!
In the editor's area levels can be imported in the text and *.xsb standard format.

SokoFun is available in 7 languages!

logo SokoMind

SokoMind is the most played Sokoban program for Windows world wide for quite some time. The program has more than 60 built-in Sokoban levels as well as 20 other "Plus" levels. *.xsb levels can be imported, but also of complete sets allows the text format levels, with a maximum level size of 33x25.
Solutions can be stored in the LURD format in separate files. Text format is also supported for level and solutions...

logo Sokoban++

A program by Joris Wit. Whole level sets can be read in and be played in different formats. The levels here really shine.

logo YSokoban

A very strong Sokoban clone by George Petrov. Perfect mouse control scheme, animated skins, good level import/export functions, good support for very large levels, and introducing an interesting "go through boxes" feature. Quirk: Access to the settings is buried in the system menu, i.e., click the icon at the left side of the main window's title bar.